A10 Pressure Relief Valve

[Brucie64]

Now that the weathers improving I guess its time to dust the cobwebs off the bike and get it serviced ready for the summer at last. However a recent article in well known bike mag got me pondering, it went on about how important a fully functional pressure relief valve is to your stead of choice.

As I have never looked at mine or indeed have ever ever paid it any notice other than to clean the knobbly protuberance next to the timing cover. Can anyone tell a self confessed mechanical idiot like myself how do you know if your relief valve is ok and is doing what it should be do*eek*.

Is there a simply test to put my mind at rest?

[muskrat]

G'day Bruce,
                 If you can't hear any main or big end noise it must be working !! The only way I know of is to fit a pressure gauge.
Cheers

[muskrat]

Second thoughts you could make up a jig out of pipe. Screw the OPRV in one end with a hole adjacent to the groove in the OPRV. then fit air line fittings to the other end and use compressor to pump up to 60Lb. It should blow off at 50 Lb. I haven't actually done this but would if I had to test one.
Cheers

[Brucie64]

My thanks Muskrat,

Hopefully I would like to know if it's gone belly up before I start to hear rumblings from down below!. Is there a recommended time at which point you should replace these for peace of mind?

[Triton Thrasher]

Is there a recommended time at which point you should replace these for peace of mind?

Original parts are often better than the new stuff available.

Some people put a Triumph type plunger valve in.  That could be a better valve, but who's to say?

[Brucie64]

Found some more data on it....

http://www.a7a10.net/oilrelief.htm

[muskrat]

Good article Bruce, I would be worried if it was fully open at 10 psi. My motors run 50 psi at 2500rpm and 20 psi at idle hot. You could try that jig vertically with oil in the tube and pressurize with air. I'm curious now and will test my spares.
Cheers

[MikeN]

You can always send it off to SRM and they will test it for you.
Mike

[Brucie64]

Or of course, for peace of mind just buy a new one from SRM.

[brackenfel]

My '61 A10 has the later (A65?) plunger type fitted rather than the one with a ball.. All I've done is simply take it out, clean it, lube it slightly & replace it..
Hopefully that will do, I can't see much point in buying an expensive but rather similar new one...

[dpaddock]

Remove the PRV from the engine, clean it and inspect it. It he ball is still round and the spring is still in one piece, reinstall the assembly and go on your way. Note that the PRV is there to protect the big ends and mains: it opens when oil pressure for them is satisfied and it then directs the excess to go to the camshaft gallery. Which is why some wag states that the camshaft has "part time lubrication."

But, don't worry about it: BSA made a good system.

Make sure you change the engine oil often to keep the internals clean.

IMOH all this SRM worship is unnecessary.

David

[Brucie64]

I agree David, I have just looked at the SRM price for the PRV and decided against it. I will as you suggest lop it out and give it a gander with the old Mk1 eyeball. Hopefully if all is well I will just slot it back in and be on my way.

Thanks Again.

[A10Boy]

You can buy a kit with ball, spring and fibre washers. Clean the gauze on the front, check the ball seat and if its in good shape you can reassemble making sure its perfectly clean. Also, dont be tempted to over tighten it into the crank case.

The main thing to keep it in good nik is regular oil changes. If any crud gets stuck under the ball, you will loose pressure to the big ends and bang... [another reason not to over do the blue hylomar]